This invention relates to a nonwoven fabric made of elastically stretchable filaments and a process for making the same.
Japanese Patent Application Disclosure No. 1998-60765 describes an elastically stretchable nonwoven fabric obtained using the known melt blown method. This known nonwoven fabric of prior art comprises a plurality of superfine, elastic and continuous component fibers heat-sealed together partially along intermittent lengths thereof and partially at intermittent points therealong. The heat-sealing is performed so that the number of lines and points along and at which the component fibers are crimped should not exceed a predetermined number. This is for the purpose of alleviating a rubber-like touch due to the elastic fibers. According to the disclosure of the Patent Application, the number of the linearly heat-sealed regions is preferably in a range of about 500xcx9c3,000/cm2 and the number of the linearly heat-sealed regions more than 3,000 will generate the undesirable rubber-like touch.
The prior art improves a strength of elastic stretchable nonwoven fabric by partially heat-sealing the superfine component fibers together along intermittent length thereof. In addition, the prior art limits the number of the heat-sealed regions to a predetermined number or less and thereby successfully relieves the nonwoven fabric of an apprehension that the nonwoven fabric might exhibit the undesirable rubber-like touch if the number of the heat-sealed regions exceeds said predetermined number. However, such nonwoven fabric of prior art is not sufficiently bulky in its thickness direction to avoid a thin and flat paper-like touch peculiar to nonwoven fabrics of this type.
An object of this invention is to relieve the nonwoven fabric comprising elastically stretchable filaments of the rubber-like touch as well as of the flat touch.
This invention to achieve such an object has a first aspect relating to an elastically stretchable nonwoven fabric and a second aspect relating to a process for making the nonwoven fabric.
According to the first aspect of this invention, there is provided an elastically stretchable nonwoven fabric comprising a plurality of thermoplastic elastomer filaments heat-sealed and/or mechanically entangled together, the filaments having crimped regions and non-crimped regions wherein each of the crimped regions has fine crimps in the rate of about 50/cm or higher.
According to the second aspect of this invention, there is provided a process for making elastically stretchable nonwoven fabric comprising the steps of:
a. blowing against thermoplastic elastomer extruded in one direction from a plurality of nozzles arranged in an array a hot blast heated at a temperature higher than a melting point of the elastomer in the one direction so that the filaments still in a molten state thereof are moved in the one direction; and
b. blowing against the filaments at a temperature between the melting point of the filaments and a room temperature a warm blast or a cold blast at a temperature at least 20xc2x0 C. lower than said melting point of the filaments so that surfaces of said filaments may be unevenly cooled and said filaments may be at least partially crimped, and to accumulate said filaments on conveyor means running transversely of said one direction wherein, in the course from said step of blowing said hot blast against said thermoplastic elastomer to accumulating said filaments on said conveyor means, said filaments are heat-sealed or mechanically intertwining together to obtain the elastic stretchable nonwoven fabric.
According to one preferred embodiment of said second aspect of this invention, an airflow of said hot blast is 0.5xcx9c2.5 Nm3/min per blow width of 1 m.
According to another preferred embodiment of said second aspect of this invention, said warm blast or cold blast is at a temperature of 90xcx9c10xc2x0 C.